Mate Choice and Parasite Resistance

For a few years now I have been involved in a unit at the University of Western Australia that consists on short research projects that get conducted individually by the students. This is not a mock exercise, but an actual research experiment that generates valuable data, and my publication with Kyana Pike (JEB, 2017) was the first one generated from one of these projects. This week I just published another paper (in Behavioral Ecology) that was half generated by a project in that unit.

Together with Larissa Assis, a student who took the unit in 2017, Leigh Simmons and I investigated female preference for male dung beetles who have higher parasite resistance. We did a cool little switch in the usual design of such experiments, and tested female preference for different males first, and then investigated their resistance to parasitic mites, in order to disentangle female choice based on the males' history of parasitism, but instead focus on whether females can assess the males' resistance to parasites per se. And we found that they can (no idea how!)!.

In the figure you can see that males who (later) had more mites (therefore they are less resistant) mated for longer with females. The order of the mating trial (first) and the experimental exposure to parasites (second) is not without problems (we discuss them in our paper), but we think we might have shed some new light on the problem. If females are in control of copula duration, and if that impacts the fertilization success of males (reasonable assumptions in my opinion), then we showed female choice for parasite resistance per se, which is cool and supports the parasite mediated sexual selection (PMSS) hypothesis by Hamilton and Zuk (1982).

Importantly, we also added data collected years ago by Janne Kotiaho (another author on the study) on the heritability of parasite resistance in these beetles, which showed strong heritability — another important assumption of the PMSS hypothesis!